1. Field of the Invention
The invention relates to a folding box having inside lining, in which case the box cutout has a prepunched opening area for extraction, which area may be ripped open, and the inside lining has a corresponding impressed window opening area and in which case at least the box cutout's opening area for extraction and the window opening area of the inside lining are connected with each other through glueing, welding, heat-sealing or the like.
2. Description of the Prior Art
Folding boxes of the kind described above are governed by two demands making claims in opposite directions. On the one hand, the boxes should be as impervious as possible (in which case distinction is made between various degrees of imperviousness, such as trickleproof, dustproof, greaseproof, steamproof, aromaproof, liquidtight and vacuum tight); on the other hand, they should guarantee easy opening, controlled emptying of the product contained therein and also, as far as possible, reclosing. In order to meet the last-named demand, they are provided with a prepunched opening area for extraction, which area may be ripped open, in the box cutout and with a corresponding impressed window opening area in the inside lining. The impressions of the inside lining can, however, in their turn, result in leakages. Cardboard is, as a rule, used for the box cutout. The material of the inside lining determines the imperviousness. A paper foil, plastic foil, metal foil, plastic-coated paper foil, plastic-coated metal foil or the like can be used for this.
It is obvious that special significance is attached to the impressing of the window opening areas on the inside lining foil when producing the folding boxes in order to meet the demand for imperviousness. "Impressing", to all practical purposes, means a slight slitting of the inside lining foil without piercing it. As a result of the impressing, the window opening area should come loose from the rest of the inside lining in a defined shape when the opening area for extraction, which is provided on the box cutout and with which the said window opening area is preferably connected through glueing, is ripped open and should remain stuck on the opening area for extraction. The impressing of the window opening areas on the inside lining foil is therefore carried out in a separate operation before the inside lining is united with the box cutouts. This is described, by way of example, in Patent No. 31 29 496 belonging to the Applicant.
Previously, considerations were based on the fact that only one single-layer inside lining foil can be impressed in such a way that it meets the demands described above. After the inside lining foil had been united with a box cutout, the latter was then erected, folded and glued. Care was thereby taken to see that two border areas of the single-layer inside lining foil came to lie side by side or one upon the other in such a way that a tubular form emerged for the inside lining and this was in order to coat the interior space of the folding box completely with internal lining. Previously, the border areas of the internal lining lying together were not connected in the case of the folding boxes considered here, that is, in the case of such boxes having opening area for extraction and window opening area, so that a weak point for the imperviousness of the folding boxes, which was striven for, emerged.
The underlying object of the invention is to improve folding boxes of the kind described by way of introduction to the effect that the level of imperviousness is increased.